Many in situ techniques exist for recovering hydrocarbons from subsurface reservoirs. One technique is called Steam-Assisted Gravity Drainage (SAGD) and employs a pair of vertically-spaced horizontal wells drilled into a reservoir. High-pressure steam is continuously injected into the overlying injection well to heat the hydrocarbons and reduce viscosity, causing the heated hydrocarbons and condensed water to drain under the force of gravity into the underlying production well. Multiple SAGD well pairs typically extend in parallel relation to each other from a well pad.
In SAGD operations, steam generation and water treatment are typically performed in a central processing facility, while the well pairs are located in remote hydrocarbon recovery areas that include at least one well pad and several SAGD wells. Production fluids recovered from the production wells are also pumped from each remote hydrocarbon recovery area to the central processing facility for treatment. Production fluids are typically water-hydrocarbon emulsions and can also include vapours. The pipeline infrastructure between the central processing facility and remote hydrocarbon recovery areas is thus designed and operated to accommodate large flow rates of steam and production fluid. High pressure steam pipelines running over long distances can be costly to install and maintain, and high flow rate production fluid pipelines require large pipes and pumps to enable transportation of the hydrocarbons and water.
In the central processing facility, there are various units for treating the production fluid in order to recover the hydrocarbons as well as treat the produced water phase to enable reuse in steam generation. Typical steam generators, such as Once-Through Steam Generators (OTSG) and drum boilers, can be large and expensive and can be shared by more than one remote hydrocarbon recovery area and/or multiple well pads.
Generation of steam at the central processing facility and transportation of steam and production fluids between the central processing facility and remote hydrocarbon recovery areas can lead to various inefficiencies and costs.
Various challenges still exist in the area of SAGD hydrocarbon recovery, steam generation as well as water treatment and recycling.